chore(deps): bump sphinxcontrib-htmlhelp from 2.0.4 to 2.1.0

Bumps [sphinxcontrib-htmlhelp](https://github.com/sphinx-doc/sphinxcontrib-htmlhelp) from 2.0.4 to 2.1.0.
- [Release notes](https://github.com/sphinx-doc/sphinxcontrib-htmlhelp/releases)
- [Changelog](https://github.com/sphinx-doc/sphinxcontrib-htmlhelp/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinxcontrib-htmlhelp@2.0.4...2.1.0)

---
updated-dependencies:
- dependency-name: sphinxcontrib-htmlhelp
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

docs/requirements.txt

@@ -4,7 +4,7 @@ sphinx-autodoc-typehints==1.23.0
 sphinx-rtd-theme==2.0.0
 sphinxcontrib-applehelp==1.0.8
 sphinxcontrib-devhelp==1.0.6
-sphinxcontrib-htmlhelp==2.0.4
+sphinxcontrib-htmlhelp==2.1.0
 sphinxcontrib-jsmath==1.0.1
 sphinxcontrib-programoutput==0.17
 sphinxcontrib-qthelp==1.0.7